Reciprocal screeds for finishing concrete



April 1, 1969 A. M GALLQ 3,435,740

RECIPROCAL SCREEDS FOR FINISHING CONCRETE Sheet Filed Dec. 2. 1966 INVENIOR Lloyd A. McGoll ATTORNEYS Sheet 2 of 5 April 1, 1969 L. A. M GALL.

I RECIPROCAL SCRBEDS FOR FINISHING CONCRETE Filed Dec. 2, 1966 v w o :QE v mm E 8 M A w o Q U M \SRFEFE.

ATTORNEYS mm wmmm y mm. 9 R. MN R um MM 3 a mm mm m ms \w m E L N f I 8 v 2 i m E P April 969 L. A. MGGALL 3,435,740

nncrraocm. SCREEDS FOR FINISHING CONCRETE Filed Dec. 2, 1966 Sheet 4 of 5 INVENTOR is, Lloyd A. McGoll ATTORNEYS A ril 1, 1969 1.. A. Nl GALL 3,435,740

RECIPROCAL SREEDS FOR FINISHING CONCRETE Filed Dec. 1966 I Sheet '5' of 5 E 38 III! E v' I 1 a:

FIG. I2

INVENTOR Lloyd A. McGoH ATTORNEYS United States Patent 3,435,740 RECIPROCAL SCREEDS FOR FINISHING CONCRETE Lloyd A. McGall, San Antonio, Tex., assignor, by mesne assignments, to Ruby Industries Inc., Austin, Tex., a

corporation of Texas Filed Dec. 2, 1966, Ser. No. 598,723 Int. Cl. E01c 19/42 US. CI. 94-45 9 Claims ABSTRACT OF THE DISCLOSURE A reciprocal concrete pavement finishing screed of lightweight construction and formed in longitudinal sections so as to be readily portable, the sectional construction permitting variation of the length of the screed in accordance with the width of the pavement. Each section is unitary and includes a self-supporting frame portion having a pair of longitudinal, reciprocal screed elements sus pended therefrom, the frame portions and screed elements of adjacent sections being detachably secured to one another to provide a composite frame and a pair of screed assemblies. Each section is of triangular, transverse configuration and has a trio of lower longitudinal frame members for slidably supporting the screed elements outboard thereof, the center frame member only being common to both elements. Adjustable fasteners suspend each screed element for independent adjustment. The screed has means at its ends for mounting upon tracks and varying its elevation.

This invention relates to new and useful improvements in reciprocal screeds for finishing concrete.

In finishing the surface of concrete pavement of the bridge, highway, street and other large area type, it is essential to provide camber and other contours skewed from the horizontal for drainage, smoothness and safety at and between inclinations, declina-tions, curves and various combinations thereof in adapting the pavement to the available roadbed. Although it is customary to finish such pavement mechanically, an entirely satisfactory finishing apparatus or screed has not been developed heretofore since the pavement varies in width and contour and, usually, is subjected to high speed and heavy traffic as well as heavy loads. Even at moderate speeds, abrupt changes of contour are detrimental to the pavement as Well as the vehicle and can be dangerous under adverse weather conditions.

The finishing apparatus or screed of the present invention, although of relatively simple structure, facilitates the formation of an optimum surface on a concrete pavement of the bridge, highway, street or other large area type irrespective of the required configuration of the pavement. The novel screed is of relatively lightweight construction and is formed in alined, longitudinal sections so as to be readily portable, the sectional construction permitting variation of the length of said screed in accordance with the width of the pavement. In addition to end sections which may be detachably connected to each other, the screed has one or more end sections capable of being mounted alone or with other sections between the intermediate sections. Each section is unitary and includes a self-supporting frame portion having a pair of longitudinal, reciprocal screed elements suspended therefrom for engagement with the pavement, the frame portions and screed elements of adjacent sections being adapted to be detachably secured to one another to provide a composite frame and a pair of screed assemblies. In order to provide maximum strength and stability with minimum weight, each of the screed sections is triangular in transverse configuration and has a trio of longitudinal frame ice members at its base for slidably supporting the pair of screed elements outboard thereof, the center frame member only being common to both screed elements and providing the requisite rigidity to the slidable mounting of said screed element. A plurality of adjustable fasteners are provided for suspending each screed element whereby the same may be readily adjusted independently of adjacent sections and rigidly secured in adjusted positions. Other features of the invention are the provision of means at the outer ends of the end sections of the screed which permit the mounting of said screed upon tracks for movement longitudinally of the pavement, the variation of the elevation of said screed in accordance with the desired thickness of the pavement as well as for free movement of said screed relative to said pavement, and for supporting one or more workmen to manipulate said screed and closely observe the finish applied thereby.

A construction designed to carry out the invention will be hereinafter described, together with other features of the invention.

The invention will be more readily understood from a reading of the following specification and by reference to the accompanying drawings, wherein an example of the invention is shown, and wherein:

FIG. 1 is a broken, side elevational view of one end portion of a reciprocal concrete screed constructed in accordance with the invention,

FIG. 1-A is a view, similar to FIG. 1, of the opposite end portion of the screed,

FIG. 2 is a horizontal, cross-sectional view taken on the line 22 of FIG. 1, partly broken away,

FIG. 2-A is a top plan view of the opposite end of the screed, partly broken away,

FIG. 3 is an enlarged, end elevational view of the screed,

FIG. 4 is an enlarged, transverse, vertical sectional view taken on the line 44 of FIG. 1-A,

FIG. 5 is an enlarged, broken, exploded, perspective view of a portion of one of the reciprocal screed assemblies,

FIG. 6 is an enlarged, transverse, vertical, sectional view showing the mounting of one of the reciprocal screed assemblies,

FIG. 7 is a view, similar to FIG. 4, taken on the line 7- 7 of FIG. 1,

FIG. 8 is an enlarged, perspective view of the upper end portion of one of the frame sections,

FIG. 9 is a view, similar to FIG. 8, of a portion of one of the screed assemblies,

FIG. 10 is an enlarged, vertical, longitudinal, sectional view taken on the line 10'10 of FIG. 2-A,

FIG. 11 is an enlarged, detail view of one of the turnbuckles,

FIG. 12 is an enlarged, end elevational view, partly in section, of the screed in an adjusted position, and

FIG. 13 is an underside plan view, partly broken away, of the screed in another adjusted position.

In the drawings, the numeral 10 designates the elongate, generally horizontal, openwork frame of a reciprocal concrete screed embodying the principles of the invention and having an engine or motor 11 and a speed reducer 12 for reciprocating a pair of screed assemblies 13 which are suspended from the frame so as to extend longitudinally thereof and which are adapted to be utilized in finishing the surface of concrete pavement 'P (FIGS. 1 and LA) of the highway, street and other large area type. The frame 10 is of elongate, rectangular configuration in plan (FIGS. 2 and 2-A) and of upright, narrow, triangular contour in end elevation (FIGS. .3, 4 and 7), said frame being formed in alined, longitudinal sections, such as 14, 15, 16 and 17, to permit variation of the length of the screed. An upper or top, coextensive, longitudinal member 18 extends centrally of each of the frame sections 14-17 and is connected at spaced intervals to a trio of lower or base, coextensive, longitudinal members 19, and 21, which are disposed in equally-spaced, parallel relationship as best shown in FIGS. 47, by a plurality of upright, transversely-inclined members or struts 22 and diagonal, longitudinally inclined members or braces 23. Each of the longitudinal frame members 18-21, struts 22 and braces 23 are in the form of a hollow, square tube to provide maximum strength with minimum weight. Preferably, the top frame member 18 has its flat surfaces extending horizontally and vertically and the flat surfaces of the base frame members 19-21 are disposed at 45 angles. The upright struts 22 extend only between the top frame member and the lateral or outer base frame members 19 and 21, while some of the diagonal braces 23 between said top member and the center base member 20 of the end frame section 14 are omitted to accommodate the motor 11, speed reducer 12 and other oscillating mechanism. In order to provide maximum rigidity and strength with minimum weight, the upper and lower ends of adjacent struts and braces converge at substantially common points including the end portions of the frame sections.

As best shown in FIGS. 4, 7 and 8, a flange 24 is mounted on the inner end of each top member 18 of each of the end frame sections 14 and 16 and on both ends of said member of the intermediate sections 15 and 17 to permit detachable connection of said sections. For the same purpose, an elongate, flat plate extends transversely between and joins the inner ends of the base members 19-21 of each of the end frame sections and both ends of said members of the intermediate sections (FIGS. 47). The end flanges 24 and plates 25 are adapted to be fastened together by suitable means 26, such as nuts and bolts, so as to dispose the frame sections 15 and 17 between the sections 14 and 16 or to secure the latter frame sections directly to each other. As shown, the end section 16 may be of very short length relative to the other frame sections in order to permit its use with 'any reasonable number of sections. Horizontal cross bars or members 27 extend between and connect the base members of the frame sections at suitable intervals, and, preferably, at or adjacent the points of convergence of the lower ends of the struts 22 and braces 23 to reinforce the frame (FIGS. 2, 2-A, 4, 6 and 7).

An upright, triangular plate 28, complementary to the transverse contour of the frame 10, overlies the outer end of each of the end sections 14 and 16 of said frame and may have its inclined, upright margins reinforced by upwardly-converging angle bars 29 extending between the outer ends of the top frame member 18 and the base frame members 19 and 21 (FIGS. 13). The top frame member of each of the end sections may project beyond the end plate 28 and have a horizontal, lateral extension 30 to provide a handle. A pair of upright, parallel guide bars or tracks 31, which are angular in cross-section, are mounted on the lower portion of each end plate for slidably confining the upright plate or portion 32 of a substantially right angular carriage 33 therebetween. The horizontal portion or platform 34 of each of the carriages 33 projects outwardly from the lower end portion of each end plate 28 and may be reinforced by a pair of upright, diagonal straps 35 extending between the platform and the upright plate 32 of each carriage and having flanges 36 projecting laterally outward from their upper ends for overlying engagement by the lower ends of a pair of elongate bolts or screwthreaded rods 37. A pair of alined, verticallyspaced nuts or screwthreaded eyes 38 are secured to each end plate for receiving and maintaining each of the bolts 37 in adjusted positions to limit downward movement of each end plate relative to its carriage.

For lifting the end plates 28 so as to elevate the frame 10 relative to the carriages 33, a jack 39 may be mounted on a horizontal bracket or shelf 40 which is secured to the upright plate of each carriage and to and between the straps 35 in overlying relation to the platform of each carriage (FIGS. l-3). Each jack 39, when in use, is adapted to bear upwardly against an angular, reinforced bracket 41 fastened to and projecting horizontally outward from each end plate. Each carriage platform 34 is of greater length and width than the upright plate 32 of the carriage and is of sufficient size to permit a workman to stand thereupon. An inverted, underlying channel 42 extends transversely of the intermediate portion of each carriage platform and is detachably fastened thereto by a suitable nut and bolt 43. Each channel 42 has a pair of spaced bracket assemblies 44 secured thereto and depending therefrom for rotatably supporting a pair of flanged rollers 45 having their horizontal axes of rotation extending longitudinally of the frame 10. The rollers 45 are adapted to ride upon suitable tracks, such as timbers T, which extend longitudinally of and are disposed laterally outward of the side forms F for the pavement P, so as to support the frame above said forms and pavement. Upon releasing the elongate bolts 37 and actuation of the jacks 39, the frame 10 may be raised relative to the carriages 33 so as to position said frame at the desired elevation. Retightening of the bolts into engagement with the strap flanges 36 maintains the frame in its adjusted position.

The screed may be propelled along the tracks or timbers T by a pair of winches 46 having supporting brackets 47 upstanding from and mounted on the outer end portions of the top frame members 18 of the end frame sections 14 and 16 adjacent the handles 30 (FIGS. 1, l-A, 2A and 3). A cable 48, having a hook 49 on its free end, is carried by each winch 46 and is adapted to be trained around an upright pulley 50 which is suitably mounted on a horizontal cross bar or member 51, 52 (FIGS. 2 and 2A) at the lower portion of the frame 10 in adjacent, spaced relation to the end plate 28 of each end frame section. Each pulley 50 has its axis of rotation extending longitudinally of the frame so that the free end of the cable 48 may extend transversely of said frame for anchoring at remote fixed point (not shown). Due to this arrangement, manipulation of the winches causes the screed to travel longitudinally of the tracks or timbers T when the free ends of the cables are anchored. At the outer end portion of the frame section 14, horizontal angle bars or members 53 extend transversely of the base frame members for supporting a pair of parallel, spaced angle bars or members 54 which extend longitudinally of said frame section for supporting an elongate, rectangular plate 55 (FIGS. 1 and 2). The motor 11 and speed reducer 12 are suitably mounted on the plate 55. Although the motor is shown as having electrical connection with a switch 56 mounted on the adjacent end plate, it is readily apparent that an internal combustion engine could be utilized and would be preferable at most places of use.

Each screed assembly 13 is formed in alined, longitudinal sections 57, 58, 59 and 60 which are of substantially the same length as the frame sections 14-17 and each of which includes a horizontal screed element 61 depending below the frame It) for riding on the forms F and smoothing the surface of the concrete pavement P (FIGS. 1 and 1-A). The screed elements 61 are in the form of elongate tubes which are rectangular in crosssection and of greater width than depth. Complementary ferrules 62 (FIGS. 5 and 10) telescope within adjacent ends of the screed elements or tubes for connecting said elements or tubes to one another in longitudinal alinement so as to provide a continuous smooth exterior. Each of the sections 57-60 of one of the screed assemblies includes a plurality of horizontal, transversely extending tie bars or members 63 having their outer ends overlying the screed element 61 of said section and their intermediate portions underlying the base frame members 19 and 20 (FIGS. 4-6). An inverted U-shape bracket 64, of a width slightly greater than the screed element, is secured to and depends from the outer end of each tie bar 63 for confining engagement with the upper portion of said element. For suspending the screed element 61 from the frame members 19 and 20, an adjustable bolt 65 has its lower end portion projecting through each end portion of each tie bar, the bracket 64 of the outer end of said bar and the upper wall of said element. Each bolt 65 is screwthreaded through a nut 66 overlying and secured to each end portion of each bar and carries another nut 67 in overlying, spaced relationship for coacting with the head of the bolt to clamp one end of an angle bar or member 68 therebetween, the angle bar having horizontal and upstanding flanges and extending transversely of the frame members 19 and 20. Preferably, an inverted angle 69 overlies and is secured to each end of each angle bar 68 to provide an open box, in coaction with the flanges of the bar, for receiving the upper end portion of each bolt 65 and positioning its head above said bar for easy access.

Each angle bar is slidably connected to each of the frame members 19 and by a pair of coacting, upper and lower guide brackets 70 which engage around the member and have horizontal, lateral flanges 71 for connection by screws 72 and nuts 73. The upper bracket 70 of each pair of brackets may have a grease fitting 74 at its apex to facilitate sliding movement of the brackets relative to the frame members. For connecting the tie and angle bars 63 and 68 of each of the sections 5760 of one of the screed assemblies to one another, a pair of elongate, parallel, spaced angle bars 75 is secured to the undersides of the angle bars between the frame members 19 and 20 so as to overlie said tie bars and extend longitudinally of the screed assembly section. The inner ends of the elongate angle bars 75 of the end screed assembly sections 57 and 60 and both ends of the elongate angle bars of the intermediate screed sections 58 and 59 are connected by short angle bars 76 extending transversely there-between (FIGS. 4-6 and 9) to permit fastening together of said elongate bars of adjacent screed assembly sections by nuts and screws 77. As best shown in FIGS. 5 and 6, recesses 78 are provided in the lower margins of the flat plates to accommodate the elongate angle bars and the longitudinal reciprocation thereof. The sections 5760 of the other screed assembly 13 are identical to the foregoing except that the intermediate portions of the tie bars 63 and angle bars 68 underlie the frame members 20 and 21 rather than the frame members 19 and 20 and are connected to said members 20 and 21 by said angle bars and the brackets 70 (FIGS. 14 and 7). Manifestly, the transverse angle bars 68 and guide brackets 70 coact with the longitudinal angle bars 75 of each screed assembly section 5760 to provide a slidable subframe for slidably suspending the tie bars 63 of each said section from the frame members 19 and 20 or 20 and 21.

As shown by the numeral 79 in FIGS. 1 and 2, a coupling connects the drive shaft of the engine or motor 11 to the input shaft of the speed reducer 12. The latter has its drive shaft 80 projecting laterally from each side thereof so as to extend transversely of the frame 10 toward the screed assemblies 13. A crank arm 81 is fastened to each end of the drive shaft 80 and extends diametrically of or at an angle of 180 relative to the other crank arm. Each crank arm 81 has its outer end pivotally connected by a bearing 82 to one end of an elongate rod or pitman 83 which extends longitudinally of the frame and has a bearing 84 on its other end for pivotal connection with a bracket or yoke 85 secured to and upstanding from the pair of elongate angle bars 75 of one of the screed assemblies between a pair of its bars 68. Each yoke 85 may include a pair of longitudinal, upright plates 86 connected in parallel, spaced relationship by short cross bars 87 so as to straddle the bearing 84 of one of the pitmans 83. Due to the opposed relationship of the crank arms, one of the screed assemblies 13 is reciprocated forwardly when the other screed assembly is reciprocated rearwardly whereby the assemblies offset or counterbalance the longitudinal thrust of each other.

Although the elements or tubes 61 of adjacent sections 57-60 of each screed assembly are connected by the ferrules 62, it is readily apparent that the adjustability of the bolts 65 permits variation of the camber as well as the vertical angularity of the screed assemblies relative to the frame. In other Words, the entire screed assemblies 13 may be inclined with respect to the horizontal or one or more screed elements may be inclined relative to one or more elements of the same assembly. Also, the screed elements 61 have sufiicient flexibility so as to be capable of undergoing limited bending movement to permit the application of a slight downward as Well as a slight upward camber. The camber of the screed assemblies may be controlled by means of turnbuckles 88 (FIGS. 1-1A) connected in the top frame members 18 at suitable intervals, such as every five or six feet. A turnbuckle 88 is not required in the end frame section 16 due to its short length and no turnbuckles are mounted in the end frame section 14 above the oscillating mechanism, which includes the motor or engine 11, speed reducer 12, pitmans 83 and yokes 85, although turnbuckles are provided at the remaining portion of said section inwardly of said mechanism. Even though only one of the turnbuckles is shown, it is contemplated that each of the longer frame sections will have one or more turnbuckles depending upon the length of the section.

One of the turnbuckles 88 is illustrated in detail in FIG. 11 and includes a rod or stud bolt 89 having its end portions screwthreaded in opposite directions for engagement with nuts 90 secured to the ends of spaced portions of one of the frame members 18 so as to extend in axial alinement therewith. A nut or other enlargement 91 is fixed on the medial portion of the rod 89 to facilitate turning thereof to vary the effective length of said rod which is adapted to be held in adjusted positions by a lock nut 92 screwthreaded on one of its end portions for engagement with one of the nuts 90. It is noted that the engagement between the ferrules and screed elements is suflrciently loose to permit limited movement of adjacent elements relative to one another. Usually, the camber is upward and may be obtained by means of shims 93 as well as by the turnbuckles. In fact, the shims provide the primary adjustment of upward camber and auxiliary or secondary adjustment of said camber is obtained by manipulation of the turnbuckles 88. As shown in FIG. 8, the shims 93 may be complementary to the end flanges 24 of the top frame members 18 and are adapted to be clamped between connected flanges by the bolts and nuts 26. For a downward camber, similar shims may be interposed between the end plates 25 of the base frame members 19-21.

As shown in FIGS. 2, 2-A and 13, each carriage platform 34 has a row of openings 94 extending medially thereof and longitudinally of the screed for coacting with the nut and bolt 43 to secure one of the channels 42 thereto in adjusted positions and permit variation of the distance between the forms F and tracks T. In addition, the use of a single fastener permits the channel to be pivoted into nonparallel relation to the transverse axis of the screed (FIG. 13) when it is desirable or necessary to propel the screed obliquely or at a skew to the forms and tracks. Each channel 42 is adapted to be clamped in adjusted positions to its carriage platform 34 by a pair of set screws 95, one of which extends upwardly through an opening 96 adjacent each end of the channel for hearing against the underside of the platform (FIG. 12). A nut 97 is secured to the underside of the channel in alinement with each opening 96 to permit adjustment of each set screw 95. Manifestly, the set screws allow inclination of each channel 42 and the plane of its rollers 45 relative to the carriage 33 without interfering with the mounting and adjustment of said carriage. Since the screed elements 61, usually, are set when said elements are resting on a support, the elements of one of the assemblies 13 may not have the exact desired elevation realtive to the forms F whereby it is frequently necessary to raise one of the screed assemblies relative to the other. Also, it is sometimes desirable or necessary for the leading screed assembly to be at a higher elevation than the trailing screed assembly.

The foregoing description of the invention is explanatory thereof and various changes in the size, shape and materials, as well as in the details of the illustrated construction may be made, within the scope of the appended claims, without departing from the spirit of the invention.

What I claim and desire to secure by Letters Patent is:

1. A reciprocal screed for finishing concrete pavement of the bridge, highway, street and other large area type including:

an elongate rectangular frame having a triangular transverse configuration,

the frame having a plurality of self-supporting sections,

including a pair of end sections, adapted to be connected in longitudinal alinement,

means at the outer end of each end frame section supporting the frame for movement transversely thereof,

each frame section being unitary and having an upper member and plurality of lower spaced members extending longitudinally thereof,

means for detachably fastening the adjacent ends of the upper and lower longitudinal members of adjacent frame sections to one another,

a plurality of upright members extending between and connecting the upper longitudinal member to the lower longitudinal members of each frame section,

a pair of substantially coextensive screed elements ex tending longitudinally of each frame section for engagement with the pavement,

a slidable subframe suspending each screed element from the lower longitudinal members of each frame section for lengthwise reciprocation,

means for detachably fastening the adjacent ends of the subframes of adjacent frame sections to one another,

a plurality of adjustable fastening means attaching each screed element to each subframe to permit variation of the relative elevation and angular relationship of said screed element as well as limited bending thereof,

means for detachably connecting the adjacent ends of the screed elements of adjacent frame sections upon the fastening together of said frame sections to provide a pair of screed assemblies substantially coextensive with said frame,

an oscillating mechanism mounted on one of said frame sections above its lower longitudinal members and having driving connections with each subframe for reciprocating the screed assemblies longitudinally of said frame, and

means mounted on the outer end of each end frame section for varying the elevation of said frame relative to the supporting means.

2. A reciprocal screed as set forth in claim 1 including:

at least one means in each of the upper longitudinal members of certain of the sections of the frame for varying the effective lengths of said members whereby a downward as well as an upward camber may be applied to said frame sections.

3. A reciprocal screed as set forth in claim 1 wherein:

the means for varying the elevation of the frame relative to the supporting means of each end section of said frame includes carriage means projecting longitudinally from the outer end of each of said end frame sections and slidably connected thereto for relative upright reciprocation,

said supporting means depending from the carriage means,

means for reciprocating each end frame section relative to its carriage means, and

means for securing each end frame section in adjusted position relative to its carriage means.

4. A reciprocal screed set forth in claim 1 including:

an upright plate at the outer end of each end section of the frame,

a carriage slidably connected to each upright end plate for relative upright reciprocation and having one of the supporting means depending therefrom,

the means for varying the elevation of said frame including means for reciprocating each end plate relative to its carriage, and

means for securing each end plate in adjusted positions relative to its carriage.

5. A reciprocal screed as set forth in claim 1 wherein:

each slidable subframe includes means extending transversely of the frame and having slidable connection with two of the lower longitudinal members of each section of said frame to provide a positive guide for the lengthwise reciprocation of each screed element.

6. A reciprocal screed as set forth in claim 1 wherein:

each of the lower longitudinal members of each section of the frame functions as a support for one of the screed elements of said frame sections, and

said screed elements are disposed laterally outward of said frame section.

7. A reciprocal screed as set forth in claim 1 wherein:

the lower longitudinal members of each section of the frame includes at least a trio of members,

each subframe including means extending transversely of said frame and having slidable connection with an outer and an inner lower frame member of the trio to provide a positive guide for the lengthwise reciprocation of each screed element.

8. A reciprocal screed as set forth in claim 1 wherein:

each slidable subframe means extending transversely of the frame and having slidable connection with the lower frame members of each section of said frame,

each adjustable fastening means for attaching each screed element to each subframe including upright bolts rotatably supported by the transverse means of each subframe so as to depend therebelow,

screwthreaded means having connection with said screed element for adjustable engagement by the bolts, and

means for securing said bolts against rotation in adjusted positions.

9. A reciprocal screed as set forth in claim 1 wherein:

each slidable subframe includes a plurality of means extending transversely of the frame and having slidable connection with the lower longitudinal members of each section of said frame,

each transverse means projecting laterally outward of said frame section and having one of the adjustable fastening means at its outer end for connecting each screed element thereto.

References Cited UNITED STATES PATENTS I Maxon 94-45 JACOB L. NACKENOFF, Primary Examiner. 

